Time, Speed & Distance
Aptitude

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Q.

A train traveling at 100 kmph overtakes a motorbike traveling at 64 kmph in 40 seconds. What is the length of the train in meters?

 A.

1777 meters

 B.

1822 meters

 C.

400 meters

 D.

800 meters

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Solution:
Option(C) is correct

Note:

When a train overtakes another object such as a motorbike, whose length is negligible compared to the length of the train, then the distance travelled by the train while overtaking the motorbike is the same as the length of the train.

The length of the train:

= distance travelled by the train while overtaking the motorbike 

= relative speed between the train and the motorbike × time taken

In this case, as both the objects i.e., the train and the motorbike are moving in the same direction, the relative speed between them = difference between their respective speeds = $100−64=36$ kmph

Distance travelled by the train while overtaking the motorbike 

=36 kmph ×40 seconds.

The final answer is given in meters and the speed is given in kmph and the time in seconds. 

So let us convert the given speed from kmph to m/sec.

1 kmph = \(\dfrac{5}{18}\) m/sec

Therefore, 36 kmph = \(36\times \dfrac{5}{18}=10\)m/sec

Relative speed = 10 m/sec. 

Time taken = 40 seconds.

Therefore, distance travelled =$10\times 40$= 400 meters


(2) Comment(s)


Vejayanantham TR
 ()

Sorry, .4*1000 = 400m



Vejayanantham TR
 ()

Time = Distance/speed

Distance = Length of the train

T = D/100-64

40/60*60 = D/36

Converting to Metre => .4 *100 = 400m